Electromagnetic device



July 8, 1930. J. ox 1,770,131

ELECTROMAGNET I C DEVI CE Filed Jan. 4, 1928 ATTORNEY Patented July 8, 1930 UNITED STATES PATENT OFFICE FLORIAN JOSEPH FOX, 0]? BALDWIN, NEW YORK, ASSIGNOR TO AMERICAN BOSCH MAGNETO CORPORATION, OF SPRINGFIELD, MASSACHUSETTS, A CORPORATION 01 NEW YORK ELECTROMAGNETIC DEVICE Application filed January 4, 1928.

This invention relates to electromagnetic devices, and more particularly to means for adjusting the position of the armature therein.

The object of this invention is to provide readily accessible means for adjusting the armature and comprising, generally, means for imposing varying pressures on a rockable support so as to rock the armature and thus adjust the position of the armature between the pole shoes.

The invention within the broad principle thereof is susceptible of numerous modifications, but for the purposes of this application and also because it has been satisfactorily employed in practice, the accompanying drawings illustrate the preferred embodiment of the invention, in application, as an example, to, an electromagnetic pickup for phonographs.

Fig. 1- is a transverse cross section of the electromagnetic device embodying the invention;

Fig. 2 is a cross section of Fig. 1;

Fig. 3 is a ing plate;

Fig. 4 is a perspective view of a needleholding armature;

Fig. 5 is a perspective view of a rockable support or bracket; and

Fig. 6 is a perspective view of a sheet of rubber or cushion adapted to be disposed between said armature and bracket.

Throughout the drawings like reference characters indicate like parts.

The electromagnetic device is enclosed in a removable casing 1 secured to the device by the acorn nut 2 on the screw 3. Within the casing is the usual U-shaped magnet 4, pole shoes 5 and coil 6.

The armature 7 consists of a flattened elongated stem 8 disposed between the pole shoes and secured in a diamond shaped transverse member 9 adapted to beheld in place and to be rocked between the supporting plate 10 (Fig. 3) and the rockable bracket or support 11 by varying the lateral pressure on said support 11. The upper and lower knife-edges of the transverse member rest on the line 2-2 perspective view of the support Serial No. 244,441.

respectively in similarly shaped grooves 12 in said plate 10 and grooves 21 formed in shoulders 22 on said support 11.

A piece of rubber 13 is adapted to be placed between the transverse member 9 and the shoulders 22 of the support 11.

The lower end of the stem 8 is tubular to receive a playing needle 14. In order to hold the needle in said stem, a set screw 15 is provided which threads axially through the transverse member and abuts against the needle.

The stem 8 and transverse member 9 may be cast integrally or otherwise joined to gether.

The plate 10 is disposed between the pole shoes, and the grooves 12 therein receive the upper edge of the transverse member 9, the casing being split at this point to permit reception and free rocking motion of the transverse member, as will be explained later. The plate is further provided with three holes. the center one of which is for the purpose of permitting the stem to pass through it and up between the upper ends of the pole shoes, and the lateral holes are employed to mount the plate on the screws 16, 16.

- The screws 16, 16 also pass through the v lower flanges of the pole shoes 5 and casing 1. Nuts 17, 17 are mounted on said screws to secure the plate 10, pole shoes and casing together. Another pair of nuts 18, 18 cooperate with nuts 19, 19 to retain the rockable support or bracket 11 on said screws 16, 16, and to permit also the adjustment of said bracket for the purpose of positioning the stem between the shoes. This adjustment is made by turning the nuts 18, 19, which rock the bracket 11 in a vertical plane. The rocking movement of the bracket is transmitted to the transverse member 9 and causes it to rock in a horizontal. plane, which in turn causes the stem to move from one pole shoe to the other. The normal operating position of the stem is, of course, centrally of the pole pieces, and normally, if the bracket or support 11 is in a truly horizontal plane with respect to the-device, the stem will be positioned between the pole pieces. If not, the stem'may be moved into such position by op- Elli Gem

erating one set of nuts 18, 19 so as to move one of the lateral extensions further up or down on the screw.

After the plate 11 has been adjusted on the screws so as to position the stem between the pole shoes, the nuts are screwed down, or up as the case may be, on said plate and. tightened to keep said plate in adjusted position and prevent it from rocking or movin {)nly upon loosening the nuts can this be done, and then only for the purpose of rocking said plate to adjust the position of the stem. 'When the plate is adjusted as aforesaid it may be considered as substantially integral or ri 'id with the armature. However, the stem is free to vibrate, though obviously the transverse member cannot because of the damping eli'ect of the plate and the rubber strip 13. This is so presumably because the vibrations of the needle are transmitted to the molecules of the armature and said vibrations are transmitted intermolecularly to the stem, the latter behaving like a vibrating member having its pivot at the point where the stem meets the transverse member. As the vibrations travel up the stem, they presumably increase in amplitude and are effective to cause electromagnetic flux variations between the pole shoes.

Because it is necessary to balance or equalize the pressures against the armature in order to position the stem exactly between the pole pieces, by means of a pressure exerted on both lateral extensions 20, I call this manner or adjusting, for convenience and for the purposes of defining the term both in this specification and claims, a bilateral adjustment.

The parts of the device are first assembled without regard to the position of the stem between the shoes, adjustment of the armature being made after such assembly. It will be understood that tightening both sides of the rockable support 11 also controls the amount of damping of the armature.

The invention is capable of being em-- bodied in loud speaker units and other telephonic and telegraphic devices.

Having described my invention, what I claim is:

1. In an electromagnetic device, an armature comprising a vibratable stem, 5, support therefor having perforated lateral extensions adapted to be mounted on screws attached to said device, and adjustable nuts mounted on said screws to retain the support and armature in position and be adjusted to exert variable pressures on said extensions so as to adjust the position of the stem between the poles of the magnet.

2. In an electromagnetic device, a needleetaining armature comprising a vibratable stem, a support therefor having perforated lateral extensions adapted to be mounted on screws attached to said device, and adjustable nuts mounted on said screws to retain the support and armature in position and ber attached to said armature and supportedby a plate having lateral extensions, and means disposed on said extensions for r0cking said plate and thereby rocking said member and armature.

5. An electromagnetic pickup comprising a magnet, a coil, pole shoes, an armature disposed between said shoes, a transverse member having knife-edge contact between supporting plates, one 0i said plates having lateral extensions, and means disposed at said extensions for rocking said plate.

In testimony whereof I afiix my si ature.

FLORIAN JOSEPH OX. 

